Projectile



March 1, 1960 QLIN 2,926,612

PROJECTILE.

Filed Jan. 13, 1955 INVENTOR. Oi-N M. 0|. IN

AGENT PROJECTILE John M. Olin, Alton, 11]., assignor to Olin Mathieson Chemical Corporation, Alton, 111., a corporation of Virginia Application January 13, 1955, Serial No. 481,619

2 Claims. (Cl. 102-925) This invention relates generally to ammunition and more particularly to a novel projectile for ammunition cartridges.

Small arms cartridges are ordinarily provided with a lead projectile. Such cartridges are particularly advantagcous for hunting purposes in rural areas because of the density and softness of the projectile but are hazardous in urban or other populated areas because of their elfectiveness over relatively long ranges. Various types of projectiles including projectiles formed from powdered iron have been proposed for target shooting and other purposes in these populated areas but none of these projectiles have had the combined properties of maximum effectiveness at short ranges and relatively ineffectiveness at long ranges. Moreover, some of the projectiles do not function satisfactorily in automatic guns and tend to shatter upon striking the target which may result in a large number of particles of metal ricocheting from the surface of the target.

It is therefore an object of this invention to provide cartridges for small arms with a projectile which is effective at relatively short distances and relatively ineffective at greater distances. A further object of this invention is to provide a projectile for small arms cartridges which will function satisfactorily in all types of firearms and is adapted for use in thickly populated areas. A still further object of this invention is to provide a projectile which can be fired from a cartridge at a high velocity and which will follow, a fiat trajectory to a target at relatively short distances. Another object of this invention is to provide a cartridge for small arms with a projectile which is lead free and is not dangerous over great distances.

These objects as well as others will become more apparent from the following description with reference to the accompanying drawing in which:

Figure 1 illustrates one embodiment of this invention; and

Figure 2 illustrates another embodiment having another shape suitable for small arms projectiles.

In accordance with this invention the foregoing objects are accomplished, generally speaking, by providing an aluminum projectile having an adherent surface coating of an oxide of aluminum. The coating must be at least microns in thickness which is greater than the thickness of the protective coating formed on aluminum when it is exposed to air. It is therefore to be understood that the term surface coating when used herein and in the appended claims includes only those coatings which are at least 10 microns in thickness. The coating may be applied by conventional chemical methods or it may be formed by conventional anodizing procedures. Only that portion of the projectile which will engage the rifling of the barrel requires the coating but in practice it is ordinarily more practical and convenient to coat the entire projectile.

It has been discovered that an adherent coating of an oxide of aluminum having a minimum thickness of at but it has been found that the surface film provided by 2,926,612 Patented Mar. 1, 19 60,

ICE

least 10 microns improves the functioning in a rifle of a metal cartridge having an aluminum projectile. If the, aluminum projectile does not have such a coating the cartridge case after firing will not'extract properly from automatic guns. The case is only partially removed from the chamber or is not released by the extraction mechanism.

No positive explanation is available of why a cartridge case which is provided with a projectile of this invention will extract satisfactorily from a semi-automatic gun after the cartridge has been fired while the case of the cartridge having an untreated aluminum projectile will not extract properly. It is believed, however, that the difference in gun performance is dueto the rate of application of pressure to the projectile when the cartridge is fired. Pressure-time curves were obtained with caliber and with cartridges otherwise similar except that the.

surface of the projectile was not treated. A study of these pressure-time curves revealed that an equivalent or greater energy was imparted at the guns muzzle to the aluminum projectiles having a coating of at least 10 microns of aluminum oxide than was imparted to the untreated projectiles even whena lesser amount of propellant was used in the cartridges having the treated projectile than in those having untreated projectiles. This would indicate that the friction between the bullet and gun barrel was decreased by anodizing the surface of the bullet. As the projectile passes from the guns chamber into the barrel, the rifling cuts into or indents the surface this invention is beneficial even though this occurs. The grooves thus formed appear to be lined with the oxide of aluminum. It may be that the poorextraction of cases from cartridges hav ng an unprotected aluminum projectile is due to the fact that too much energy is required to start and move the projectile down the gun barrel and thus too little remains to operate the extraction mechanism of the automatic rifie. This presumption is based primarily on theory, however, and may not be .the'true explanation of the phenomena which produced the improved characteristics of the cartridge having. the pro jectile of this invention over cartridges having aluminum projectiles which have not been so treated.

Referring to the accompanying drawing, one type of aluminum projectile suitable for small arms cartridges such as for caliber .22 is illustrated in Figure 1. Projectile 1 has a continuous coating 2 about 10 microns thick of an oxide of aluminum over its entire surface. In this particular embodiment the nose portion 3 of projectile 1 and the heel portion 5 are of less diameter than the band 4 which will engage the rifling of the barrel. Heel 5 is provided with a concavity 6 to improve the gas seal in the barrel and the functioning of the projectile.

The embodiment illustrated in Figure 2 is also suitable for small arms cartridges and differs from that of Figure 1 in that the nose 3 at its posterior end is of substantially the same diameter as the cross-sectional diameter of rifling band 4. Heel 5 is of lesser diameter and like the heel of the embodiment shown in Figure 1 is adapted to fit snugly in the cartridge case mouth. Heel 5 is also provided with a concavity 6. In this particular embodiment it is essential that surface coating 2 cover the posterior part of nose 3 which will engage the rifling of the" barrel. The surface of band 5 should also be coated with the oxide and for this reason for most purposesjt I I immersed about 30 seconds in a solution of from about 4 to 5 ounces sodium hydroxide per gallon of' water maintained at a temperature? of about 180 F. The projectiles are then removed from this solution and rinsed in water to remove any sodium hydroxide clinging thereto and they are thereafter anodized about 30 minutes in a 15% sulfuric acid-in-water solution at a current. density of 12 to 15 amperes per square foot. The temperature of this solution during the anodizing treatment is maintained within the range of about 68 F. to about 74 F. This anodizing treatment may take place in any conventional anodizing equipment in which the projectiles can be made the anode. The anodized projectiles are removed from the solution and rinsed in water after which they are immersed about 30 minutes in. a solution of about one-half ounce nickel acetate per gallon of water at a temperature of about 200 F. and. again rinsed in water and air dried.

It is important to provide the projectile with a, con: cavity at the posterior end thereof such as shown in the drawing. The purpose of this hollow heel is to prevent. the gases from escaping by the projectile during its travel through the gun barreL Unlike lead projectiles, aluminum projectiles do not upset properly and seal the gun barrel unless a hollow heel is provided. This hollow heel is particularly important if the cartridge is to be fired in one of the riflles having a chamber adapted to fire cartridges of different lengths. For example, many rifles chambered for caliber .22 cartridges have a chamber of suflicient length to accommodate the longest cartridge available in this caliber, i.e., the .22 long rifle but it is sometimes desirable to be able to fire the caliber .22 short cartridge in such a rifle. Unless the aluminum short projectile is provided with a hollow heel the gas seal in such rifles is very poor and consequently the velocity of the projectile is seriously affected.

The projectiles may be formed from aluminum wire by cutting the same into slugs and thereafter swaging the slugs into the desired shape. It is also contemplated that the projectiles may be molded from aluminum if desired or they may be formed by any other suitable means known to the art.

Although the projectile provided by this invention is particularly well suited for use in caliber .22 it is also useful in any caliber where a light weight projectile effective at short ranges but substantially ineffective at long ranges is required. The bullet may assume any other conventional shape but shapes shown in Figures 1 and 2 are ordinarily preferrd for caliber .22 cartridges. Likewise, any other adherent chemical compound of aluminum on the surface of the projectile, such as, for example, a fluoride thereof can be utilized for the purposes of the invention.

The invention has been. described in considerable detail in the foregoing for the phrpose of illustration but various modifications canbe made therein hythose skilled.

in the art withoutdeparting-from th'e'spirit and' sc o'pe of the invention except insofar as the invention limited by the appended claims;.

What is claimed is:

12 An aluminum small oaliber projectile to be driven through a small arms gun barrel bore and having a nose and a heel and intermediate thereof rifling means to snugly engage said. bore said means. comprising a portion of the surface of"; said projectile, and insane dim crease the muizle velocity of's'aid projectile; the last said, means.comprisinganartificially applied coating'of. an adherent aluminum oxide having minimum thickness of the order of' 1.0 microns andinot substantially in. excess thereof on at least said portion of the surface of said projectile.

2. An aluminum projectile of .22" caliber to be driven through a barrel bore and having anose and-a hollow heel and intermediate thereofrifiii'ig means to snugly engage said bore, said means comprisin a portion of the surface of said projectile, and means? t6 increase the muzzle velocity of said projectile, the last said means comprising an adherent aluminum oxide coating substantially 10 microns thick on at lea-st said portion of the surface of said projectile.

lieferenc'es citeirin'mefiie: ofth'is patent UNITED STATES FATENTS 

2. AN ALUMINUM PROJECTILE OF .22 CALIBER TO BE DRIVEN THROUGH A BARREL BORE AND HAVING A NOSE AND A HOLLOW HEEL AND INTERMEDIATE THEREOF RIFLING MEANS TO SNUGLY ENGAGE SAID BORE, SAID MEANS COMPRISING A PORTION OF THE SURFACE OF SAID PROJECTILE, AND MEANS TO INCREASE THE NUZZLE VELOCITY OF SAID PROJECTILE, THE LAST SAID MEANS COMPRISING AN ADHERENT ALUMINUM OXIDE FILM COATING SUBSTANTIALLY 10 MICRONS THICK ON AT LEAST SAID PORTION F THE SURFACE OF SAID PROJECTILE. 